Polyolefin wet spinning process



Aug. 7, 1962 w. JURGELEIT 3,048,465

POLYOLEFIN WET SPINNING PROCESS Filed Sept. '7, 1960 2 Sheets-Sheet 1FIG! 22"PUMP INVENTOR. WOL EGANG JURGELEIT ATT'Y S Aug. 7, 1962 w.JURGELEIT POLYOLEFIN WET SPINNING PROCESS 2 Sheets-Sheet 2 Filed Sept.7, 1960 ATT'YS United States Patent 3,048,465 POLYOLEFIN WET SPINNINGPROCESS Wolfgang Jurgeieit, Coraopolis, Pa., assignor to VereinigteGlanzstofi-Fahriken A.G., Wuppertal-Elberfeld, Germany Filed Sept. 7,1960, Ser. No. 54,406 Claims priority, application Germany June 16, 195615 Claims. (CI. 18-54) This invention relates to spinning solutions andto processes or methods for spinning and further processing polyolefinfilaments so as to increase the rate of filament production and toimprove in other ways processes for producing fine denier polyolefinfilaments. In particular, the invention is concerned with the so-calledwet-spinning process for the production of polyolefin filaments in whichthe polyolefin is first dissolved in an organic solvent, the filamentsthen spun from the hot spinning solution and solidified, after which thesolvent is extracted from the filaments in a liquid bath and thefilaments stretched for molecular orientation and/or diameter reduction.

This application is a continuation-in-part of my copending applicationsSerial No. 76,688, filed September 23, 1958, and now abandoned, andSerial No. 664,289, filed June 7, 1957, and now abandoned.

In a known wet-spinning process for the manufacture of high-pressurepolyolefin filaments, the polymer is spun as a solution in a suitableorganic solvent, e.g., as described in US. Patent No. 2,210,771, and theextruded or spun filament emerges from a spinneret into a socalledprecipitation bath in which the filament solidifies because ofextraction of the solvent with a liquid which is inert to the polymerbut miscible with the solvent. Suitable precipitation bath liquidsinclude many alcohols and ethers, and various ketones and esters havealso been used. The function of the precipitation bath is to withdraw atleast part of the solvent from the extruded polymer spinning solutionsuch that the spun filaments will have sutficient strength to undergosubsequent operations, e.g., those in which the filaments are drawn orstretched for molecular orientation. An inadequate removal or extractionof the solvent, either during precipitation or in subsequent steps priorto stretching the filament for molecular orientation, as in conventionalwet-spinning processes, yields filaments which are still semi-liquid andwhich tend to stick together and are very easily deformed.

Certain wet-spinning processes have been developed to overcome some ofthese disadvantages byremoving a major portion of the solvent in theprecipitation bath. However, in order to avoid poor fiber properties,this more complete extraction of the solvent must be carried out veryslowly, thereby requiring additional space for the bath and/or arelatively inadequate production capacity. 7

It is particularly difficult 'in these prior processes to obtain a finedenier filament together with a high production capacity. Thewet-spinning process is desirable because it is usually possibletoproduce finer deniers and higher tensile strengths than when merelyspinning the polymer in its molten form and in the absence of anysolvents. However, wet-spinning is not only slower than melt-spinning,but many of the solvents and precipitating 3,048,465 Patented Aug. 7,1962 ice liquids are difiicult to work with and in some cases present aserious explosion hazard.

An object of the present invention is to provide new and improvedprocesses for the production of polyolefin filaments so as to overcomethe disadvantages of prior wet-spinning and melt-spinning processes.

A specific object of the invention is to provide simplified processesfor producing fine denier polyolefin filaments of high tensile strengthat a more rapid rate, i.e., a higher production capacity.

Another particular object of the invention is to produce polyolefinfilaments from spinning solutions in processes wherein the polymersolvent can be very rapidly and substantially completely extracted fromthe spun filaments without damage to fiber properties. In a preferredform of the invention, a specific extraction liquid is provided for thispurpose.

Yet another object of the invention is to provide improved processes inwhich the low pressure, high-molecular weight polyolefins can beadvantageously spun to provide excellent fibers for textile uses.

These and other objects and advantages of the invention are more clearlybrought forth in the following detailed description of the invention.

In the drawings:

FIG. 1 is a diagrammatic side elevation of equipment for preparing andspinning hot solutions of polyolefins into a solidification bath; and

FIG. 2 is a diagrammatic illustration of a preferred process of theinvention.

Briefly, I have found that high molecular weight polyolefin filamentscan be spun rapidly and processed into excellent filaments if a hotpolyolefin-containing spinning solution is extruded and first introduced.into a solidifying bath which contains a liquid medium inert to andsubstantially immiscible with both the polyolefin and its solvent.

The filaments are solidified in this first bath by reducing theirtemperature, the bath being maintained at a temperature below about 30C., and preferably between about 0 C. and 30 C. This cooled andsolidified filament is easily processed even though substantially nosolvent has been extracted therefrom and even can be drawn or stretchedmildly, if desired; Exemplary liquids for the solidifying bath are waterand lower alkanols, e.g., propanol and butanol.

The solvent is not extracted until after the solidifying bath, and suchextraction is accomplished before the first stretching of the filaments.I

It is especially advantageous to rapidlyand as completely as possibleextract the solvent from the cooled and solidified filament with aliquid media which is inert to the polyolefin but miscible with thesolvent such as petroleum ether, diethyl ether or, more preferably, withliquid methylene chloride which gives a surprisingly good extraction ofthe solvent. In this respect, methylene chloride is particularlyadvantageous as compared to such liquids as petroleum ether with whichthere is a danger of an explosion. The extraction and stretching stepsmay be repeated once or twice more. 7 l t More particularly, thepolyolefins spun in accordance with this invention are polymers ofmono-olefins having from 2 to 5 carbon atoms, inclusive, such as thoseproduced by the recently developed low pressure polymerization processto provide a polymer molecular weight of at least 60,000 and preferablyabove 70,000. Polyethylene and polypropylene are the preferred polymersfor filaments. Poly-butylene, polyisobutylene and polymerized pentene orisopentene can also be spun into filaments by the practice of thisinvention.

The polyolefin spinning solution is prepared by dissolving thepolyolefin in a hydrocarbon solvent selected from the group consistingof paraffins and cycloparafiins to form a spinning solution containingabout 10 to 18% by weight of the polyolefin. The hot spinning orextrusion of the filaments is then carried out at a temperature of about150 C. and 250 C., and preferably about 180 C. to 220 C., the parafiinor cycloparaffin hydrocarbon being in its liquid state at this spinningtemperature. 'It will be recognized that the hydrocarbon solvent shouldnot boil at the spinning temperature and should therefore be selectedfrom those compounds having an initial boiling point in the range ofbetween about 150 C. and 380 0., preferably above 150 C. to about 300 C.These solvents are ordinarily obtained as the intermediate to heavydistillates in the fractionation of petroleum and consist essentially ofparafiins, naph-thenes, or mixtures of paraffin and naphthene (i.e.,cycloparatfin) hydrocarbons. They are known under such commercial orfamiliar names as mineral oil, gas oil, paraffin oil,

spindle oil, White oil and the like.

The spinning head is spaced above the surface of the solidifying bath ata distance so that the freshly spun filaments pass through an air spaceof at least 5 centimeters. The air space is ordinarily in the range of510 cm. 'The production of the spinning solution and the subsequentspinning process can be carried out in the tity. The polymer isdispersed in the oil by vigorous stirring. The tank is kept at atemperature of to 20 C. by means of a cooling jacket 12. The valve inconduit 16 is opened, and the dispersion flows into the heated worm '18,which again stirs the mixture. This stirring worm is heatedto aboutl80-220 C. by a heating jacket 20; The dispersion of the polyolefinpowder in the corresponding oil' is converted, in the course of thepassage through the worm, into a clear viscous solution. This solutionis pumped by the action of the worm 18 into the spinning pump 22, heatedto about the same temperature as the solution. The solution is pumped tothe spinning head 24, and the fine filaments emerging from the nozzle 28first traverse an air space of at least 5 cm. in length and then passinto the cool solidifying bath 26.

It is an essential "feature of the present invention that the hot,freshly spun filaments of polyolefin solution at a diameter of 100-300containing at least about 82% solvent are introduced through an airspace of at least 5 cm. into a cool solidifying liquid bath which isinert to both the polyolefin and its solvent. By inert it is meant thatthe liquid in the solidifying bath is not miscible with and issubstantially a non-solvent for either the polymer or its solvent. Ofcourse, this liquid should not react chemically with the polymer orotherwise be damaging to the highly linear fiber-forming structure ofthe polymer.

Water isby far the most useful inert liquid for the solidifying bathsince it .is. the cheapest and most easily inert impurity or anti-freezeagent is added to the water to form an aqueous solution. No additionalsubstances w carbons, preferably n-propanol, n buta'nol, or sec-butanol.

The function of the solidifying bath'required by the present process isdistinct from that which is required in the usual wet-spinning process.Accordingly, the term solidifying bath is employed herein to distinguishfrom the usual so-called precipitation bath in which the primary purposeis to solidify the filament by extracting solvent rather than'by asimple cooling effect. Surprisingly, a mere cooling of the filaments inwater according to the present invention was found to provide asolidified filament of polyolefin solution having sufficient strength tobe easily handled in a spinning procedure with conventional drawing orfilament conveying apparatus.

It is a particularly preferred embodiment of the invention to follow thesolidification bath with an extraction bath of methylene chloridebecause methylene chloride gives very excellent and rapid extraction ofthe polymer solvent from the filaments. If the polyolefin spinningsolution is spun directly into methylene chloride, the excessive andrapid extraction of the solvent will prevent proper filament formationand cause the filaments to become crumbly. For this reason, it isespecially surprising that such good results could be obtained withmethylene chloride subsequent to the solidifying treatment with water inthe present invention.

Following the first solvent extraction, the filaments are stretched byan amount of 1.5 to 3 fold of the original length of the spun filamentsat a temperature between about C. and C. It is done expeditiously in awater bath heated to a temperature of 90-l00 C., preferably about 95 C.If more extraction of solvent from the filaments is necessary, theextraction step above-described is repeated. The filaments are then,again, stretched by 2 to 6 fold of the filament length just prior to thesecond stage stretching at elevated temperature, preferably at least C.,but not higher than the softening point of the filaments. The secondstretching is done conveniently by running the filaments over a heatedsurface just prior to or during the stretching stage of the process.

Although it is feasible to use a single extraction bath with the presentprocess, it is diflicult to achieve a rapid and complete extraction inthis manner, and an optimum productioncapacity cannot be realized. Thereason for this is that the solvent is first extracted near the surfaceof the filament and the time required to remove the solvent increasesdisproportionately as it becomes more difiicult to remove solvent nearerto the central portion or axis of the filament. By using more than oneextraction step, a minor portion or surface portion of the solvent canfirst be extracted quite rapidly, after which the filament can bestretched so that the solvent is again more uniformly distributedthroughout the filament. The solvent is actually believed to be exudedor distributed toward the surface of the filament by the reduction indiameter during such stretching. The content of solvent is thuspreferably reduced from about 80% or more down to not more than 70% inthis first extraction in order tjo prevent filament breakage, andusually down to around With methylene chloride, one additionalextracting step is sufficient to substantially remove the solvent, e.g.,to a content of not more than 5% by weight of the filament, andpreferably so that the filament has a residual solvent content of notmore than about 1%, usually about 0.5 to 1%. Such a two-step procedurerequires considerably less time for extraction and permits a much higherproduction capacity. Liquids other than methylene chloride such asdiethyl ether or petroleum ether ordinarily require more than twoextraction steps or much longer extraction baths so as to lose theadvantages of small space requirements and optimum production capacity.The importance of solvent extraction according to the present inventionresides in the fact that a rapid and almost complete removal of solventcan be accomplished even though such procedure is not always required.801* vent extraction is done at any suitable temperature below theboiling point of the solvent. Room temperature or ambient temperatureordinarily is adequate.

The first stretching step will most ordinarily require a drawing out ofthe fiber of up to about 2 to 2 /2 or even 3 times its original length.The final stretching after the second stage solvent extraction iscompleted most ordinarily is an additional three to six-fold elongation,such that the total stretching or elongation ratio with relation to theoriginal filament length is usually not more than about 1:9 or 1:10. Ahigh degree of stretching or drawing is possible in this process so thatvery fine denier filaments can be obtained. Both stretching steps can beaccomplished in heated liquid baths. Conventional heated bars, plates,godets or the like can also be used for the second stretching stage.Prestretching after a first extraction bath is carried out at about 90C. to 105 C., preferably in a hot water bath, while the final stretchingis best carried out at a temperature above about 110 C. but below thesoftening point of the polymer.

Various techniques in stretching are possible depending upon theproperties desired in the filament, and the amount of stretching at anyparticular point in the process can be easily determined by thoseskilled in the art. In this connection, the present invention is notconcerned with such subsequent steps as crimping, finishing, dyeing,twisting or preparation of staple fibers, but such steps are not to beexcluded.

A diagrammatic illustration of a preferred embodiment is shown in FIG. 2of the drawing. The heated polyolefin solution in parafiin and/ orcycloparafiin solvent is spun from spinneret 30 as filaments 32 of saidsolution pass through an air space into a solidification bath 34containing water at -30 C. The filaments are drawn from thesolidification bath without significant stretching into a solventextraction bath 36 of methylene chloride. The extracted filaments aredrawn into a stretching bath 38 of water at 9598 C., in which they arestretched by the desired amount.

The stretched filaments are drawn through a second solvent extractionbath 40 of methylene chloride in which substantially all of theremaining solvent is extracted from the filaments. The extractedfilaments are stretched further by the desired amount between rollerpairs 42, 44 while in contact with a heated, arcuate plate 46 at atemperature of at least 110 C. The filaments are spooled on spool 48.

The invention is further illustrated by the following examples. Theinvention is not to be limited to these examples, however.

Example I A low pressure polyethylene having a molecular weight of about150,000 is dissolved in parafiin oil (a mineral oil which is practicallyfree of aromatic compounds and has a boiling point of 220-225 C.) in aconcentration of 15% by weight. The solution is heated to a temperatureof 180 C. and extruded from a conventional spining head or spinnerethaving orifices with an individual size of ZOO/1. in diameter. Theextruded or spun filaments first pass through a short air space of about10 cm. in which about 2 to of the solvent (by weight of the filament) isgiven off by evaporation. The filaments are next introduced into a coldwater bath maintained at a temperature of about 20 C. in which thepolyethylene-containing filaments harden or solidify to form filamentscapable of being withdrawn from the bath by a conventional draw roll orconveying roll. In this water bath, the paraflin oil content of thefilaments remains practically constant, i.e., about to by weight of thefilament.

The solidified filaments are then passed or conveyed into a firstmethylene chloride bath at the same temperature as the water bath, theextraction bath being arranged as a Washing tube through which themethylene chloride can be continuously passed. The paraffin oil contentfalls to about 55% by weight of the filament in this first extractionbath. 7

The filaments are next stretched in hot water (98 C.) to about twicetheir original length and this stretching causes a slight solvent lossdown to about 48-50% by weight of the filament. The remaining solvent isthen removed in a second washing tube, again with methylene chloride, toa residual content of 0.5l% by weight of the filament. Once again thefilament is subsequently stretched four times its length for an over-allelongation of eight times its original spun length.

The resulting filaments have excellent textile properties of tensilestrength and a fine denier.

Example [I Polyethylene of the molecular weight 150,000 is dissolved inparaifin oil (boiling point 260 to 280 C. 6.5 mm.) at 200 C. to form a14% strength spinning solution and spun through a 30-hole spinning headwith openings of 200 diameter each. The filaments emerging from thenozzle pass through a 10 cm. air space and enter a solidification bathof propanol maintained at 20 C. The filaments run approximately 2 /2meters in this bath, are then conducted into an extraction bath, 4meters long, of petroleum ether, a petroleum fraction consistingprimarily of C H and C H hydrocarbons, B.P. 40-60 C., at roomtemperature and are thereupon immediately subjected to preliminarystretching to about three times their original length. After thepreliminary stretching, the filaments are extracted again in a petroleumether bath and afterwards again stretched to three times their lengthfor a total stretch of 9 times their original lengh.

Example III Polypropylene of the molecular weight 150,000 is dissolvedto form a 12% spinning solution in commercial paraffin oil at 180 C.This spinning solution is extruded through a l2-h0le spinning head, asdescribed in the preceding example, and conducted through a 6 cm. airspace into a solidification bath of propanol at 10 C. About 8.2 cc. perminute of the spinning solution emerge through the 12 openings of thespinning head, each of 200 diameter. The filaments emerging from thesolidification bath traverse a petroleum ether extraction bath and thenpass through a stretching device in which they are stretched to 2 /2times their original length. The filament rate into the stretchingdevice amounts to 20 m./ min., the filament rate out of the device 50m./min. After passing through the stretching device the threads arewashed in ether and spooled.

The threads obtained in this manner can be further stretched above C.,and twisted on stretch-twist machines, such as are used, for example, inthe processing of polyamides or linear polyesters. After completion ofthe final stage, the stretching amounts, altogther, to about 9 times theoriginal length. The threads obtained have a strength of 70 Reisskilometer (7.8 g./ denier) at 15% extension and an individual titer ofabout 3 den.

Example IV 60 g. of polyethylene powder of average molecular weight500,000 are dissolved by heating to C. in 400 g. of a colorless mineraloil with a boiling point of 204 to 227 C. This spinning solution is spunthrough a 30-hole spinning head, as described in the preceding examples,into a cold solidification bath of propanol at 20 C. Between the nozzleopening and the surface of the solidification bath there is an air spaceof about 8 cm. in length. The filaments run for about 2 /2 metersthrough the solidification bath and then enter a petroleum etherextraction bath of about 6 meters in length. They are then stretched to2.4 times their original length in a hot water bath at 95 C., which is 4meters long. Thereupon, the filaments again run through a petroleumether extraction bath of about 6 meters in length, and are then spooledin the usual manner.

The spooled filaments are stretched later to 3.3 times their spooledlength on a hot plate (112) in a stretchtw-ist machine, as described inExample 111.

The extraction bath can be made elfectively in the form of 3%. metertubes, into which the filaments are introduced from above, are conductedover a guide roller at the bottom and are finally led out at the upperend. In order to avoid a larger concentration of the polyolefin solventin the extracting liquid, it is continuously drawn off underneath and,in distilled form, returned above.

Example V 150 g. of polyethylene powder of the molecular weight of150,000 are dissolved in 1 kg. of white oil, corresponding to a 15%spinning solution. The further processing of the spun filamentscorresponds exactly with Example IV. The filaments obtained have a finalstretch of 9 times their original length, and a strength of 125 Reisskilometer (13.9 g./denier) at 3.8% extension. The titer of theindividual filaments amounts to 1.8 den.

The present invention avoids most if not all of the many disadvantagespreviously encountered with a wet-spinning of polyethylene or otherpolyolefins. The bath liquids employed are relatively inexpensive andmuch easier to handle than those required in prior processes. There areno explosion hazards in the present process. While polyethylene is avery inexpensive raw material and has very valuable fiber properties,particularly with the low pressure polymer, polypropylene is moredesirable from the standpoint of fiber properties even if moreexpensive. The present invention permits both to be produced in a highlyconvenient and practical commercial process with a high productioncapacity.

The essential features of my invention are outlined as follows. A l-l8%solution of a polyolefin of at least 60,000 molecular weight in asolvent of parafiin and/or naphthene hydrocarbons is spun through an airspace of at least cm. into a solidification bath maintained at about0-30 C. The function of this bath is to cool the spun filaments ofpolyolefin solution without substantial extraction of the solvent or thepolyolefin.

The solidified filamentary solution is then extracted to remove asubstantial part of the polyolefin solvent. The extracted filaments arestretched at 90-105" C. They are extracted again to remove morepolyolefin solvent so that the solvent content of the filaments iscertainly less than 10%, preferably less than 5%, and most optimallyless than one percent on a weight basis. Though not essentialin allcases, the filaments thereafter can be stretched again up to a totalamount of stretch not exceeding 9 or 10 times the original length of thespun filaments.

The invention is hereby claimed as follows:

1. In a process for the production of a polyolefin filament in which thepolyolefin has a molecular weight of at least 60,000 and is spun from anorganic solvent spinning solution, the solvent extracted from thefilament and the filament stretched for fiber orientation, the stepswhich comprise: extruding the polyolefin spinning solution conrtainingfrom about 10 to not more than 18% by Weight of said polyolefin throughan air space of at least five centimeters into a solidifying bathcontaining a liquid medium inert to both the polyolefin and its solvent;cooling and solidifying the spun filament substantially without solventextraction in'said liquid medium which is maintained at a temperature ofabout 0 C. to 30 C.; extracting the solvent from the filament in asecond bath containing a liquid which is inert to the polyolefin butwhich is miscible with the organic solvent; and stretching thesolventextracted filament.

2. In a process for the production of a polyolefin filament in which thepolyolefin has a molecular weight of at least 60,000 and is spun from anorganic hydrocarbon solvent spinning solution, said hydrocarbon solventbeing selected from the group consisting of parafiins and cycloparafiinsthe solvent is extracted from the filament and the filament is stretchedfor fiber orientation, the steps which comprise: extruding thepolyolefin spinning solution containing from about 10 to not more than18% by weight of said polyolefin through an air space of at least fivecentimeters into an inert aqueous solidifying bath; cooling andsolidifying the spun filament in said aqueous bath which is maintainedat a temperature of about 0 C. to 30 C.; extracting said solvent fromthe filament in a second bath comprising methylene chloride; andstretching the solvent-extracted filament.

3. A process as claimed in claim 2 wherein the polyolefin is a lowpressure, high-molecular weight polymer of a mono-olefin having from 2to 5 carbon atoms, inclusive.

4. A-process for the production of a fine denier polyolefin filamentwhich comprises: dissolving a low pressure polymer of a mono-olefinhaving from 2 to 5 carbon atoms, inclusive, and a molecular weight of atleast 60,000 in a hot organic hydrocarbon solvent for said polymer, saidsolvent being selected from the group consisting of paraflins andcycloparalfins; extruding the resulting spinning solution as a filamentthrough an air space of at least five centimeters into an inert aqueoussolidifying bath; cooling and solidifying the spun filament in saidaqueous bath which is maintained at a temperature of about 0 C. to 30C.; subsequently extracting a part of the solvent from the filament in amethylene chloride bath and stretching the solidified filament; andrepeating said extracting and stretching steps at least once.

5. A process as claimed in claim 4 wherein the polyolefin ispolyethylene.

6. A process as claimed in claim 4 wherein a minor portion of thesolvent is extracted in a first methylene chloride bath followed bystretching in a hot water bath; and the solvent is then furtherextracted to not more than 5% by weight of the filament in a secondmethylene chloride bath followed by additional stretching to obtain ahighly oriented fine denier filament.

7. A process as claimed in claim 6 wherein the residual amount ofsolvent in the filament amounts to less than about 1% by weight afterleaving the second methylene chloride bath.

8. A process for the production of a fine denier polyethylene filamentwhich comprises: dissolving a low pressure polymer of polyethylenehaving a molecular weight of at least 60,000 in a hot hydrocarbonsolvent selected from the group consisting of paraffins andcycloparafiins and in a quantity of about 10 to not more than 18% byweight of the resulting spinning solution; extruding said spinningsolution at a temperature of between about 150 C. and 250 C. into aninert aqueous solidifying bath; cooling and solidifying the spunfilament in said aqueous bath which is maintained at a temperature ofabout 0 C. to 30 C.; subsequently extracting the solvent from thesolidified filament in a methylene chloride bath; stretching thesolidified filament; and

repeating extracting and stretching steps at least once.

9. A process as claimed in claim 8 wherein a minor portion of thesolvent is extracted in a first methylene chloride bath followed bystretching at a temperature of about C. to C., and the solvent is thenfurther extracted to not more than about 5% by weight of the filament ina second methylene chloride bath followed by additional stretching at atemperature of above about C. but below the softening point of thepolymer.

10. A process as claimed in claim 9 wherein the residual amount ofsolvent in the filament amounts to less spawns 9 10 than about 1% byweight after leaving the second 15. A process as claimed in claim 1wherein said methylene chloride bath. liquid in said second bath isdiethyl ether. 11. A process as claimed in claim 1 wherein said liquidmedium is a lower alkanol containing not more References Cited In thefile of thls Patent than four carbons. 5 UNITED STATES PATENTS 12. Aprocess as claimed in claim 1 wherein said 2,210,771 Myles Aug. 6, 1940hqmd medlum PYOPaHPI' 2 354 745 Dreyfus Aug 1 1944 13. A process asclaimed 1n claim 1 wherein said 2706674 Rothrock 1955 hquid medlum 1Sbutano1 22 237 Iwamae in F b 4 195 14. A process as claimed in claim 1wherein said 10 2825721 Hogan 1958 liquid in said second bath ispetroleum ether.

I corrected below.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,048,465 August 71 I962 Wolfgang .Iurgeleit ed that error appears inthe above numbered patters Patent should read as It is hereby certifi ndthat the said Let ent requiring correction a Column I line 24, for "T6688" read 762,688

nd sealed this 22nd day of January 1963 Signed a (SEAL) Attest: ERNESTw. SWIDER DAVID L DD Commissioner of Patents Attesting Officer

1. IN A PROCESS FOR THE PRODUCTION OF POLYOLEFIN FILAMENT IN WHICH THEPOLYOLEFIN HAS A MOLECULAR WEIGHT OF AT LEAST 60,000 AND IS SPUN FROM ANORGANIC SOLVENT SPINNING SOLUTION, THE SOLVENT EXTRACTED FROM THEFILAMENT AND THE FILAMENT STRETCHED FOR FIBER ORIENTATION, THE STEPSWHICH COMPRISE: EXTRUDING THE POLYOLEFIN SPINNING SOLUTION CONTAININGFROM ABOUT 10 TO NOT MORE THAN 18% BY WEIGHT OF SAID POLYOLEFIN THROUGHAN AIR SPACE OF AT LEAST FIVE CENTIMETERS INTO A SOLIDIFYING BATHCONTAINING A LIQUID MEDIUM INERT TO BOTH THE POLYOLEFIN AND ITS SOLVENT;COOLING AND SOLIDIFYING THE SPUN FILAMENT SUBSTANTIALLY WITHOUT SOLVENTEXTRACTION IN SAID LIQUID MEDIUM WHICH IS MAINTAINED AT A TEMPERATURE OFABOUT 0* C. TO 30* C.; EXTRACTING THE SOLVENT FROM THE FILAMENT IN ASECOND BATH CONTAINING A LIQUID WHICH IS INERT TO THE POLYOLEFIN BUTWHICH IS MISCIBLE WITH THE ORGANIC SOLVENT; AND STRETCHING THESOLVENTEXTRACTED FILAMENT.